We report the results of an experimental and theoretical study of structure formation in mixtures of phenyl-C₇₁-butyric acid methyl ester (PC₇₁BM) with high boiling octane based solvent additives 1,8-octanedithiol (ODT), 1,8-dibromooctane, and 1,8-diiodooctane obtained by evaporation of a host-solvent (chlorobenzene). Experimental studies by DSC, SAXS and WAXS methods found evidence of crystallization of fullerenes in the presence of the high boiling additives in the mixtures. A molecular dynamics simulation of a PC₇₁BM/ODT mixture revealed the self-assembly of fullerenes into sponge-like network structures.